Merge branch 'net-control-the-length-of-the-altname-list'

Jakub Kicinski says:

====================
net: control the length of the altname list

Count the memory used for altnames and don't let user
overflow the property nlattr. This was reported by George:
https://lore.kernel.org/all/3e564baf-a1dd-122e-2882-ff143f7eb578@gmail.com/
====================

Link: https://lore.kernel.org/r/20220309182914.423834-1-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/rtnetlink.c

@@ -3652,13 +3652,24 @@ static int rtnl_alt_ifname(int cmd, struct net_device *dev, struct nlattr *attr,
 			   bool *changed, struct netlink_ext_ack *extack)
 {
 	char *alt_ifname;
+	size_t size;
 	int err;
 
 	err = nla_validate(attr, attr->nla_len, IFLA_MAX, ifla_policy, extack);
 	if (err)
 		return err;
 
-	alt_ifname = nla_strdup(attr, GFP_KERNEL);
+	if (cmd == RTM_NEWLINKPROP) {
+		size = rtnl_prop_list_size(dev);
+		size += nla_total_size(ALTIFNAMSIZ);
+		if (size >= U16_MAX) {
+			NL_SET_ERR_MSG(extack,
+				       "effective property list too long");
+			return -EINVAL;
+		}
+	}
+
+	alt_ifname = nla_strdup(attr, GFP_KERNEL_ACCOUNT);
 	if (!alt_ifname)
 		return -ENOMEM;